Method of integrating a watermark into a compressed image

ABSTRACT

In accordance with one embodiment of the invention, a method is provided for integrating at least a portion of a watermark into at least a portion of a compressed image. The method of this embodiment includes encoding at least a portion of the watermark and compressing at least a portion of the image. The encoded watermark, or portion thereof, and the compressed image, or portion thereof, are combined. Of course, many other embodiments in accordance with the invention are included within the scope of the present invention.

RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 10/194,179, titled “Method of Integrating A Watermark Into ACompressed Image,” filed Jul. 12, 2002, now U.S. Pat. No. 6,608,912,which, in turn, is a continuation of U.S. patent application Ser. No.09/519,135, titled “Method of Integrating A Watermark Into A CompressedImage,” filed Mar. 6, 2000, now U.S. Pat. No. 6,449,380. The subjectpatent application is also related to U.S. patent application Ser. No.09/519,874, titled “Method of Integrating a Watermark into an Image,” byAcharya et al., filed Mar. 6, 2000, assigned to the assignee of thecurrent invention and herein incorporated by reference.

BACKGROUND

This disclosure is related to watermarking and, more particularly, tointegrating or embedding a watermark into an image, such as a compresseddigital image.

The management of information is becoming a more challenging problemwith the progress of information technology, especially in the area ofdigital imaging. Identification of ownership and/or other rights withrespect to an image when transmitted through a network, such as a publicnetwork, is receiving a great deal of attention. Furthermore,information management and the secure movement of image data arebecoming complex tasks, particularly in light of the rapid evolution ofa variety of technologies. “Digital Watermarking” may provide apotential solution to this problem.

BRIEF DESCRIPTION OF DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.Embodiments of the invention, however, both as to organization andmethod of operation, together with objects, features, and advantagesthereof, may best be understood by reference to the following detaileddescription when read with the accompanying drawings in which:

FIG. 1 is a schematic diagram illustrating one example application of anembodiment of a method of integrating a watermark into a compressedimage in accordance with the present invention;

FIG. 2 is a flowchart illustrating one embodiment of a method ofintegrating a watermark into a compressed image in accordance with thepresent invention; and

FIG. 3 is a flowchart illustrating an embodiment of a method ofrecovering the integrated watermark from a compressed image inaccordance with the invention, specifically for recovering the watermarkfrom a combined image made according to the embodiment of the inventionillustrated in FIG. 2.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of embodiments of theinvention. However, it will be understood by those skilled in the artthat embodiments of the present invention may be practiced without thesespecific details. In other instances, well-known methods, procedures,components, and circuits have not been described in detail so as not toobscure embodiments of the present invention.

Some portions of the detailed description which follow are presented interms of algorithms and symbolic representations of operations on databits or binary digital signals within a computer memory. Thesealgorithmic descriptions and representations are the techniques used bythose skilled in the data processing arts to convey the substance oftheir work to others skilled in the art. An algorithm is here, andgenerally, is considered to be a self-consistent sequence of acts oroperations leading to a desired result, and include physicalmanipulations of physical quantities. Usually, though not necessarily,these quantities take the form of electrical or magnetic signals capableof being stored, transferred, combined, compared, and otherwisemanipulated. It has proven convenient at times, principally for reasonsof common usage, to refer to these signals as bits, values, elements,symbols, characters, terms, numbers or the like. It should beunderstood, however, that all of these and similar terms are to beassociated with the appropriate physical quantities and are merelyconvenient labels applied to these quantities. Unless specificallystated otherwise, as apparent from the following discussions, it isappreciated that throughout the specification, discussions utilizingterms such as “processing” or “computing” or calculating” or“determining” or the like, refer to the action and processes of acomputer or computing system, or similar electronic computing device,that manipulate and transform data represented as physical, such aselectronic quantities, within the computing system's registers and/ormemories into other data similarly represented as physical quantitieswithin the computing system's memories, registers or other suchinformation storage, transmission, retrieval, or display devices.

Operations, such as image acquisition, encoding, manipulation,transmission, retrieval, or storage particularly involve carefulhandling of noise that may be present in one or more images and whichmay appear as perceptually disturbing artifacts. The impact of this maybe reduced by reducing the impact at the source. However, this may notalways be possible, and, furthermore, images that may be digitallycaptured may, at times, be left with remnants of noise, even after theapplication of noise reduction techniques. Techniques and processes areavailable to reduce the impact of spatial noise on still images anddigital cameras and both spatial and high frequency noise in video imagecapture systems. However, another field of image representation isreferred to as “Digital Watermarking,” in which specific signalinformation may typically be encoded as “noise.” A Digital Watermark maybe a specially encoded symbol or signature placed in the image for thepurpose of image authentication or verification or simply for encodingsecret information in one or more images.

It would be desirable to have a process or technique for encodingDigital Watermarks that was unaffected, or at least substantiallyunaffected, by the process of image compression/decompression. Oneembodiment of a method of integrating a watermark into a compressedimage in accordance with the present invention provides that capability.

Digital Watermarks, such as logos or signatures, may be introduced intothe image in a variety of ways. As one example, although the inventionis not limited in scope in this respect, the watermark itself may be,for example, a 32×32 image block of a logo or signature that may beencrypted or, alternatively, employed in the form provided. Thiswatermark signal information, or a portion of the watermark, may becombined into the image, or a portion thereof, after the image or imageportion has been compressed. This may be implemented by inserting thewatermark pixel signal values between selected pixel values or betweenselected pixel locations using a suitable technique or process.Therefore, in this example, the signal information may be intermittentlyinterspersed in the compressed image, or portion thereof. In particular,in one such embodiment, the watermark, or a portion thereof, may beencoded, the image, or a portion thereof, may be compressed, and theencoded watermark and the compressed image, or portions thereof, maythen be combined in this manner, for example.

Typically, after an image is captured by an image capture device, suchas an imager, for example, it undergoes image processing, followedusually by compression, before storage and/or transmission. To retrieveand display the image, a corresponding decompression process ortechnique is typically applied. Usually, feasible imagecompression/decompression processes or techniques are “lossy” in nature,that is, the pixel signal values of the decompressed image do notcorrespond precisely to the original image. If the Digital Watermark, inthe form of pseudo-random noise, is encoded in the image, thecompression and decompression typically will corrupt the encodedwatermark signal information and, hence, the watermark will not berecoverable for identification and/or authentication to occur.

In one embodiment of a method of integrating a watermark into acompressed image in accordance with the present invention, therefore,encoded watermark signal information is integrated into a compressedimage. Of course, as previously indicated, the watermark signalinformation may alternatively not be encoded. Furthermore, in oneparticular embodiment, some relevant signal information may also beprovided in the header, although the invention is not limited in scopein this respect. The encoded watermark signal information, therefore, iscombined in the compressed data of the compressed image, or a selectedportion thereof, such as by intermittently interspersing the watermarksignal information with the compressed image data. The watermark signalinformation may then be decoded from the compressed image either priorto decompression of the compressed image or, alternatively, during thedecompression process, depending upon the particular integrationmethodology that may have been applied during integration of thewatermark signal information with the compressed image. The decodedwatermark signal information may then be blended with the decompressedimage in a perceptually non-detectible or barely detectible manner, ifdesired, as described, for example, in the aforementioned concurrentlyfiled patent application, although the invention is not limited in scopein this respect. For example, this may not be performed.

Encryption of watermark signal information may be done by encoding theinformation in the spatial domain or the transform domain. Image orspatial domain encoding may involve random scrambling of bits with anunscrambling key similar to what has been applied in 128-bit encryptionfor Internet applications and image transmission, for example. See, forexample, “A method for obtaining digital signatures and public keycryptosystem,” ACM Commun. 1978, Vol. 21, pp120-126; “Evaluation ofselective encryption techniques for secure transmission ofMPEG-compressed bit-streams,” Alattar et al., Proc. ISCAS, pp 340-343.vol. 14, 1999; or “Combining data compression and encryption,” C.Finnila, IEEE WESCON/94, pp 404-409, although, these are merely providedas examples. Alternately, transform domain encoding may be done in anyone of a number of ways, such as with Fourier transform encoding,wavelet transform encoding, Walsh-Hadamard transform encoding, etc. Itwill, of course, be appreciated by one of ordinary skill in the art thatthese are just examples of image domain encoding and frequency domainencoding, and the invention is not limited in scope to any particularapproach. Any one of a number of currently known or later to bedeveloped approaches may be employed.

In one particular embodiment of a method for integrating a watermarkinto a compressed image, a process in accordance with the presentinvention may include the following. For an image stored as a file ofpixel signal values, for example, the compressed image file may berepresented as C(F). Let B denote a 32×32 block representing thewatermark signal information in this particular embodiment. Of course,the invention is not limited in scope to a watermark or watermark signalinformation of any particular size or shape. In this particularembodiment, watermark signal information B is encrypted. Let E(B)represent the bit stream of the encrypted block B. In this particularembodiment E(B) is divided into a series or sequence of groupings ofbits, here 8 bit “bytes,” which represent the watermark encoded signalvalues. For example,

E(B)=N ₀ N ₁ N ₂ N ₃ . . . N _(m)  [1]

where each N_(i) represents a byte in the encrypted block E(B).Therefore, E(B) is the binary digital signal representation or bits forthe encrypted block. Of course, the invention is not restricted todividing the watermark into bytes. For example, in an alternativeembodiment, the watermark signal information may be divided intogroupings of bits that comprise 4 bit nibbles instead. In thisparticular embodiment, the watermark signal information E(B) may then beincluded or combined into the compressed file C(F) using the approachdescribed hereinafter.

Here, the bytes of the encrypted watermark block E(B) are distributedover the compressed image file between selected byte locations in thecompressed image. Likewise, in this particular embodiment, the bytelocations are selected in accordance with a pseudo-random numbergeneration technique. Any one of a number of pseudo-random numbergeneration techniques may be employed, and the invention is not limitedin scope to any particular process. However, in this particularembodiment, an initial “seed” of the pseudo-random process is selectedsubstantially in accordance with the following relationship [2]:

Q←└[size[E(B)]+size[C(F)]]/1024┘

where “size[ ]” denotes the size of the file in bytes in thisembodiment. To generate the next pseudo-random number, apply thepseudo-random number generation technique using the seed equal to theexisting value of Q. Let Q now represent the newly generatedpseudo-random number.

For this particular embodiment, the encoded watermark signal informationis combined with the compressed file signal information in the followingmanner. In the compressed file C(F), insert byte N_(i) of E(B) betweenbytes B_(Q) and B_(Q+1) of the compressed image file C(F), where ivaries from 0 to m. A pixel P(m,n) may be mapped into B_(P) whereP=m*c+n, c is the number of pixels in each row, r is the number of rows,m increases from 0 to r−1 by increments of 1, and n increases from 0 toc−1 by increments of 1. By this technique, Q may be mapped to a pixellocation B_(Q), although, of course, any one of a number of othertechniques for making an assignment between numbers and pixel locationsmay be employed. Therefore, after inserting the first byte N₀ ofencrypted watermark, E(B), in this particular embodiment, for example,to generate the next byte location into which to insert the next byteN₁, apply the same pseudo-random number generation technique using theexisting value of Q as the seed. This is illustrated schematically inFIG. 1.

FIG. 2 is a flowchart illustrating the previously described embodiment,although, again, this is just one example of an embodiment in accordancewith the invention. The invention is not limited in scope to onlyimplementing this particular flowchart. For example, as illustrated inFIG. 2, in block 110 the image is compressed, and in block 120, thewatermark is encoded, in this embodiment, encrypted; however, theinvention is not limited in scope to this order of these operationsbeing performed. Furthermore, as previously described, the watermark maynot even be encoded or encrypted. In block 130, as illustrated, theinitial seed, Q, is selected, and i, a counter, is set to zero. For thisembodiment, the initial seed is selected in accordance with thepreviously provided relationship [2], although, again, the invention isnot limited in scope to this initial seed, or to using a counter, or tousing a counter that begins at zero. In block 140, a pseudo-randomnumber generation technique is applied to the initial seed, and Q isreplaced with the value generated in this manner. In block 150, aspreviously described, the byte N_(i) is then inserted in compressedimage file C(F) between bytes B_(Q) and B_(Q+1) of C(F). For thisembodiment, this process is continued until the entire encoded watermarkis combined into the compressed image, although that may not be the casein alternative embodiments. An aspect of this particular embodiment,although the invention is not limited in scope in this respect, is thesecure transfer of information. For example, for this embodiment, ifboth the sender and the receiver are familiar with the approach employedto integrate the watermark into the compressed image, then someone elseintercepting the image will generally be unable to extract or recoverthe watermark, and, therefore, will not be able to access theinformation being transmitted in this fashion. Likewise, it may bepossible for the receiver to tell if the image received by the receiverhas been intercepted and whether tampering to the image has occurred.

For the above embodiment of a method of integrating a watermark into acompressed image, there is a corresponding embodiment of a method ofrecovering a watermark or encoded watermark from a compressed image inaccordance with the present invention. For example, for the previouslydescribed embodiment, a corresponding embodiment for recovering awatermark or an encoded watermark from a compressed image includes:determining the locations of the groupings of bits, such as, in thisembodiment bytes, in the combined compressed image-encrypted watermarkfile, C_(E) (F), that correspond to the groupings of bits, here bytes,N_(i), of the encoded watermark E(B), in this particular embodiment;extracting the bytes for the encoded watermark from those respectivebyte locations in file C_(E)(F); and forming the encoded watermark fromthe extracted pixel signal values. It is noted that, of course, thewatermark extracted and formed may be a watermark subportion, and thecompressed image may be a compressed image subportion. Likewise, theencoded watermark, whether or not a subportion, may be decoded andblended with the decompressed image, whether or not a subportion, ifdesired, such as, for example, by using a technique or approach, such asone of those described in the concurrently filed aforementioned patentapplication, although, as previously indicated, the invention is notlimited in scope in this respect. For example, the decoded watermark maynot be blended with the decompressed image at all, or they mayalternatively be blended using another technique other than one of thosedescribed in the aforementioned patent application.

In this particular embodiment, due to the approach in which the bytes ofE(B) have been inserted into the combined file C_(E) (F) of thecompressed image and the encoded watermark the combined file C_(E)(F)will have a size, for example, in bytes, equal to the sum of therespective sizes of C(F) and E(B), again, for this embodiment, in bytes.Therefore, the location of the particular bytes in the compressed imagefile may be recovered. In particular, the seed for the random processpreviously described above is in accordance with the followingrelationship [3]:

Q←└size[C _(E)(F)]/1024┘

It is noted that although any pseudo-random number generation techniquemay be employed, the same pseudo-random number generation technique mustbe employed for coding and decoding for this particular embodiment.Therefore, the pseudo-random process is applied to the seed, and thatnumber is designated Q (see blocks 310 and 320 in FIG. 3). A byte N_(i)is located in the compressed image right after B_(Q) in C_(E)(F) and,therefore, it may be extracted (see block 330 in FIG. 3). After all thebytes, N_(i) of the encrypted watermark E(B) have been extracted (seeblocks 340 and 350 in FIG. 3), they may be concatenated to provide E(B).This particular embodiment is illustrated by the flowchart in FIG. 3,although the invention is not limited in scope in this respect, ofcourse.

This particular embodiment of a method of integrating a watermark into acompressed image and this embodiment of recovering an encoded watermarkfrom a compressed image provide a number of advantages. They allowsecure image data representation and secure movement of signalinformation, as previously described. Likewise, as previously indicated,the watermarks may be encoded and encrypted in either the image orfrequency domain which provides an added level of security for theseparticular embodiments. An additional level of security may be obtainedby encrypting the data placed in the image header, although theinvention is not limited in scope in this respect. Likewise, a doublelevel of encryption may be provided, in these particular embodiments,because, initially, the watermark pixel signal values may be encrypted,and, then, the choice of pixel locations in the compressed image atwhich to insert the bytes of the watermark may depend on the seed andpseudo-random number generation techniques employed. Likewise, anotheradvantage of these particular embodiments is the relative ease, in termsof computational complexity, to extract the watermark from the image andverify authenticity. Likewise, due to the nature of this particularembodiment, it is relatively easy to remove the watermark signalinformation prior to compression and decompression for imagetransmission/recovery.

It will, of course, be understood that, although particular embodimentshave just been described, the invention is not limited in scope toparticular embodiments or implementation. For example, one embodimentmay be implemented in hardware, whereas another embodiment may beimplemented in software. Likewise, an embodiment may be implemented infirmware, or any combination of hardware, software, or firmware, forexample. Likewise, although the invention is not limited in scope inthis respect, one embodiment may comprise an article, such as a storagemedium. Such a storage medium, such as, for example, a CD-ROM, or adisk, may have stored thereon instructions, which when executed by asystem, such as a computer system or platform, or an imaging system, mayresult in a method of upscaling a color image in accordance with theinvention, such as, for example, an embodiment previously described.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes andequivalents will now occur to those skilled in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

What is claimed is:
 1. A method of integrating at least a portion of awatermark into at least a portion of a compressed image to generate acombined file, the method comprising: encoding the at least a portion ofthe watermark; compressing the at least a portion of the image; andcombining the at least a portion of the encoded watermark and the atleast a portion of the compressed image to generate the combined file,the combining of the at least a portion of the encoded watermark and theat least a portion of the compressed image comprising inserting arespective groupings of bits of the at least a portion of the compressedimage, the groupings of bits being inserted at locations in thecompressed image determined based, at least in part, on a size of thecombined file.
 2. The method of claim 1, wherein encoding the at least awatermark portion comprises encrypting the at least a watermark portion.3. The method of claim 2, wherein combining the encrypted at least awatermark portion and the at least a compressed image portion comprisesdividing the encrypted at least a watermark portion into bytes anddistributing the bytes over the at least a compressed image portion. 4.The method of claim 3, wherein distributing the bytes of the encryptedat least a watermark portion over the at least a compressed imageportion comprises intermittently interspersing the bytes of the at leasta watermark portion between selected byte locations in the at least acompressed image portion.
 5. A method of integrating a watermark into acompressed image to generate a combined file, the method comprising:dividing the watermark, or portion thereof, into groupings of bits;compressing the image, or portion thereof; and intermittently insertingthe watermark bit groups throughout the compressed image, or portionthereof, at locations in the compressed image, or portion thereof,selected based, at least in part, on a size of the combined file.
 6. Themethod of claim 5, wherein the groupings of bits comprise 4 bit nibbles.7. The method of claim 5, wherein the groupings of bits comprise bytes.8. The method of claim 7, wherein intermittently inserting the bytes ofthe watermark, or portion thereof, over the compressed image, or portionthereof, comprises inserting the respective bytes of the watermark, orportion thereof, between respective, selected byte locations in thecompressed image, or portion thereof.
 9. The method of claim 5, whereinthe watermark comprises an encoded watermark.
 10. The method of claim 9,wherein the encoded watermark comprises an encrypted watermark.
 11. Amethod of recovering a watermark from a combined image file of thewatermark and a compressed image, said method comprising: determininglocations in the combined image file that include groupings of bits forthe watermark, the groupings of bits being previously inserted atlocations in the compressed image selected in accordance with apseudo-random number generation technique; extracting the bit groupingsfor the watermark from the locations; and forming the watermark from theextracted bit groupings for the watermark.
 12. The method of claim 11,wherein the watermark as formed from the extracted bit groupings is asubportion of a watermark.
 13. The method of claim 11, wherein thecompressed image is a compressed subportion of an image.
 14. The methodof claim 11, wherein the watermark is an encoded watermark.
 15. Themethod of claim 14, and further comprising: decoding the encodedwatermark.
 16. The method of claim 11, wherein the groupings of bitscomprise bytes.
 17. An article comprising: a storage medium havingstored thereon instructions to integrate a watermark, or portionthereof, into a compressed image, or portion thereof, to generate acombined file, the instructions, when executed by a machine, resultingin: dividing the watermark, or portion thereof, into groupings of bits;compressing the image, or portion thereof; and intermittently insertingthe watermark bit groups throughout the compressed image, or portionthereof, at locations in the compressed image, or portion thereof,determined based, at least in part, on a size of the combined file. 18.The article of claim 17, wherein the instructions, when executed,further result in: dividing the watermark, or portion thereof, into bytesized groupings of bits.
 19. The article of claim 18, wherein theinstructions, when executed, result in the intermittently inserting ofthe bytes of the watermark, or portion thereof, over the compressedimage, or portion thereof, by inserting the respective bytes of thewatermark, of portion thereof, between respective, selected bytelocations in the compressed image, or portion thereof.
 20. An articlecomprising: a storage medium having stored thereon instructions torecovering a watermark, or portion thereof, from a combined image fileof the watermark, or portion thereof, and a compressed image, or portionthereof, the instructions, when executed by a machine, resulting in:determining locations in the combined image file that include groupingsof bits for the watermark, or portion thereof, the groupings of bitsbeing previously inserted at locations in the compressed image, orportion thereof, determined based, at least in part, on a size of thecombined image file; extracting the bit groupings for the watermark fromthe locations; and forming the watermark, or portion thereof, from theextracted bit groupings for the watermark.
 21. The article of claim 20,wherein the instructions, when, executed, result in recovering anencoded watermark, or portion thereof, from the combined image file. 22.The article of claim 21, wherein the instructions, when executed,further result in: decoding the encoded watermark, or portion thereof.